Insulin-related peptide and neuroparsins in locust reproductive physiology
Catholic University of Leuven, Department of Biology, Belgium
The desert locust (Schistocerca gregaria) displays a fascinating type of phenotypic plasticity. In response to changes in population density the genome of these locusts can be translated in either the solitarious or gregarious phenotype. Locusts in the gregarious phenotype (or 'phase') aggregate in large swarms and migrate over large distances. In this phase the animals are devastating pest insects. An interesting target for pest control strategies is the reproductive process and this fact stimulates fundamental research in locust reproduction. In this context, our research group previously characterized an insulin-related peptide (Scg-IRP) in the desert locust. 'Quantitative real time reverse transcriptase PCR' assays were indicative for a role of Scg-IRP in female locust reproductive physiology. In addition, a neuroparsin was originally identified as an anti-gonadotropic factor in the migratory locust (Locusta migratoria) and was later suggested to be an insulin-binding factor. Subsequently, four neuroparsins (Scg-NP1-4) had also been identified in the desert locust. By means of RNA interference experiments the transcript levels for Scg-IRP and the four Scg-NPs were knocked-down in two separate experiments. The experimental design allowed for a knock-down during the period of sexual maturation and vitellogenesis. Knock-down of Scg-IRP resulted in lowered levels of vitellogenin transcripts and, accordingly, in smaller oocytes in the double-stranded (ds) RNA-treated animals. Oppositely, lowered levels of Scg-NP transcripts resulted in increased levels of vitellogenin transcripts and larger oocytes in the dsRNA-treated animals. The obtained results are indicative that Scg-IRP and Scg-NPs are regulators of the female reproductive event of vitellogenesis, although it is not yet clear whether they directly or indirectly act upon the fat body to regulate this process. Since the fat body has a well-known function as a storage organ for nutritional energy, immediate information about the animal's nutritional status is available from this organ. In addition, insulin is a conserved sensor of nutritional status. A rise in Scg-IRP transcript levels in the fat body had previously been observed in females during a period characterized by extensive growth of oocytes. Therefore we suggest that Scg-IRP regulates the nutrient-dependent process of vitellogenesis by 'sensing' the nutritional status of the animal and perhaps acting as a paracrine substance on the fat body to stimulate vitellogenesis. It should then not be excluded that the Scg-NPs exert their negative influence on female reproduction by interacting with Scg-IRP.
25th Conference of the European Comparative Endocrinologists, Pécs, Hungary, 31 Aug - 4 Sep, 2010.
(2010). Insulin-related peptide and neuroparsins in locust reproductive physiology.
25th Conference of the European Comparative Endocrinologists.
26 Aug 2010;
29 Aug 2010.
Dr. Liesbeth Badisco, Catholic University of Leuven, Department of Biology, Leuven, Belgium, firstname.lastname@example.org